Electrical wave transmission



C. D. EHRET.

ELECTRICAL WAVE TRANSMISSION.

APPLICATION FILED MAR. 12, I9I9.

Patented Dec. 20, 1921.

CORNELIUS D. EHRE'I, OF PHILAD ELPHIA, PENNSYLVANIA.

ELECTRICAL WAVE TRANSMISSION.

Specification of Letters Patent. Patented De 20, 1921 Application'flledMarch 12, 1919. Serial No. 282,166.

To all whom it may concern:

Be it known that I, CORNELIUS D. EHRn'r, a citizen of the United States,residing in the city and county of Philadelphia, State of Pennsylvania,have invented a new and useful Electrical Wave Transmission, of whichthe following is a specification.

My invention relates to a method of and apparatus for electricallytransmitting speech by recourse to carrier waves both in systems wherethe energy of those waves is radiated or otherwise transmitted throughthe natural media, and where the carrier wave is in the form of acurrent transmitted over a conductor or conductors extending between thetransmitting and receiving stations.

My inventionresides in a method of and apparatus or system forelectrically transmitting speech, or sound waves in general, whereinenergy modulated. in accordance with sound waves or speech is impressedupon the plate or anode circuits of a thermi-' onic oscillationproducing means, whereby different groups of high frequency oscillationsor. carrier waves are produced whose amplitude varies in accordance withthe speech or soundwaves, the envelop of the successive groupsrepresenting the complete message, such energy being supplied as theplate or anode circuit energy of and as distinguished from the usualdirect current source employed for energizing the plate or anodecircuit.

By such method and apparatus no high frequency or carrier wave energy isradiated or impressed upon the line conductor until the existence ofspeech or sound waves; that is to say, no high frequency energy comesinto existence or is radiated or impressed upon the line conductor untilthe microphone is actuated by speech orother sound waves.

My invention resides further in a method and apparatus or system of thecharacter referred to, wherein the telephonic current is first amplifiedbefore conversion into the hi h frequency carrier wave; energy.

y invention resides further in a method and apparatus or system of thecharacter referred to in which the high frequency or carrier wave energyproduced asdescribed is amplified before radiation thereof into thenatural media or impression thereof on a line conductor.

in the absence My invention resides further in a method and apparatus orsystem of the character referred to wherein high frequency currentmodulated .in accordance with speech or sound waves is converted intohigh frequency or carrier wave energy of different, preferably higher,frequency.- s

For an understanding of my method and for an illustration of some of thevarious forms my apparatus may take, reference is to be had to theaccompanying drawing, in which:

Figure 1 is a diagrammatic View of apparatus embodying my invention andsuitable for carrying out my method.

Fig.2 is a diagrammatic View of a modified form of apparatus suitablefor a simplified'method of carrying out my invention.

Fig. 3-is a diagrammatic view of a modified form of apparatus embodyingmy invention and suitable for carrying outmy method.

Referring to Fig. 1, a microphone m is connected in circuit with asuitable'sourceof current, as a battery a, in the primary of atransformer 25 whose'secondary is connected directly to the circuit ofthe grid 9 of an amplifier A of suitable type, in this instance ofthermionic type having in association with the grid 9 the anode or platep and the filament or cathode f rendered incandescent by current fromthe battery I). In the grid circuit; may be included if desired orsuitable, a device cwhich may be either a condenser or a battery, aswell understood in the art. In the plate circuit of the amplifierformation, but preferably a step-uptransformer delivering currentatpotential high enough, as regards the smallest amplitude of the voicecurrent it is desired shall be transmitted, to equal and preferablyexceed the lowest potential suitable for operating the anode circuits ofthe oscillator O. The opposite ends of the transformer secondary. areconnected, respectively, to the plates or anodes p and p of a thermionicoscillator 0 comprising, in addition, the grid 9 and incandescentfilament or cathode f. Connected across thesecondary of the transformert, are the condensers C and C preferably variable to attain equalcapacity, or, in any event, to cause oscillations of the same frequencyin and by cooperation with the inductance L, whose one terminal connectsto a point between the condensers C and C and to a variable mid-point onthe secondary of the transformer t,, and whose other terminal isvariable and connected to the filament f. The grid circuit is coupled topart of the inductance L by the variable inductance Z. In the gridcircuit may be employed if suitable or desirable a condenser c. a

In inductive relation with the inductance L is the variable transformersecondary L whose one terminal connects through the variablenon-inductive resistance 7*, which may be adjusted to suitable value orwhich may be entirely cut out, to the grids g, g of the high poweramplifiers A A any number of which may be connected in parallel witheach other as indicated, as by parallel connection of their plates,grids and filaments. For energizing the plate circuits may be providedthe battery'or other source of current al and in the grid circuits maybe connected the battery 6 with its negative terminal presented to thegrids. Connected across the grid circuit, upon closure of the switch e,is a variable condenser C for tuning the grid circuit to the frequencyof the oscillations derived from the secondary L However, it will beunderstood that .either or both the condenser C and the resistance 1"may be omitted.

connectedthrough an adjustable inductance L to the antenna or radiatingstructure R of a radio system. Or the transformer secondary L mayconnect to any suitable line conductor \or line conductor systemextending between transmitting and receiving stations.

The operation as follows:

Uttering speech or sound waves against the microphone m Varies thecurrent from the battery a, and the resultant current having sound waveor speech modulation is transformed by the transformer t and deliveredto .the amplifying apparatus A,

. which amplifies the telephonic energy to any suitable'fidegree. Forthis purpose a plurality of amplifier devices A maybe employed, eitherin parallel or in cascade.

The amplifiedenergy is then impressed by transformer t upon the anode orplate circuits of the oscillator O, with the result that,

all the undulations or frequencies of positive sign or polarity from thesecondary-of the transformer t are converted by one of The plate circuitof. the amplifiers A A, includes the adjustable transformer primary L incircuit withthe anode circuits, for example, that includplitude inaccordance with speech or sound waves, the telephonic energy being theonly energy supplied to the plate or anodecircuits, as distinguishedfrom the ordinary case where a battery or the like is in the anode orplate circuit and the telephonic energy employed merely to vary thepotential of the grid of the thermionic oscillator.

*ith an oscillator which employs a battery or the like in the platecircuit, with the potential of the grid altered in accordance withspeech to vary the amplitude of the oscillations produced from energy ofthe battery, oscillations are continuously produced without regard tothe fact whether or not speech or sound waves are being uttered againstthe microphone which controls the potential of the grid; and in a systememploying such an oscillator the high frequency oscillations, or carrierwave is being continuously radiated or impressed upon I the lineconductor.

By my method and apparatus, however, as described, the high frequencyoscillations are not existent or produced except when the microphone isactuated.

The oscillations so produced directly by conversion from the telephonicenergy are then suitably amplified, if desired, to practically anypower; and as such, impressed uponthe radiating system B of a radiosys-' tem or analogous system employing the natural media, or upon aline conductor extending to the receiving station.

It will be understood that the amplifier also that the amplifiers A A,may be omitted. I

The omission of these amplifiers is'indicated in Fig. 2, where with theinductanceL the oscillator O intervenes a second oscilla- 1 tor 0 of a'known type employing in its plate circuit abatteriy d, which suppliesthe 115 A may be omitted; and it will be understood I ing modulated bythe microphone m through the potential control of the grid 9 oroscillator 0 These high frequency oscillations are then transmittedthrough the transformer t, to the oscillator 0, wherein the half wavesor oscillations of positive sign are converted into high frequencyoscillations of the same or different frequency, higher or lower, in thecircuit of one of the anodes, as 39,, while the half waves oroscillations of negative sign are converted into oscillations of suchdifferent frequency inthe circuit of the anode 79,. The energy of theoscillations of this second frequency, which also are modulated inaccordance with the sound waves or speech uttered against microphone m,are impressed through transformer L, L either upon a line conductor orupon the radiating system or structure R. For example, the frequency ofthe oscillations produced by oscillator 0 may be 10,000, 20,000 or30,000 cycles per second, or

more or less, while the frequency of the oscillations produced by theoscillator 0 may be any suitable higher frequency, for example, upwardlyto 500,000 cycles per second, or

more.

OfFigs. 1 and 2,.it is characteristic that in the anode or platecircuits of the oscillator 0 no battery or other source of energy ispresent which, if .present, would cause conaccordance with speech untilthe microphone m is actuated by speech'or sound waves, or other means.

What I claim is: l

1. The combination with a thermionic oscillator comprising anodes, atransformer secondary connected thereto, grid structure and anelectron-emitting body, inductance and capacities in the circuits ofsaid anodes,

a coupling between the circuit of the grid structure and the anodecircuits, said capacities connected in series across said secondary, aconnection from between said capacities to said inductance, and meanssupplying modulated energy to said transformer including a source ofcontinuous current, and means controlling the current of said source inaccordance with sound waves.

2. A thermionic oscillator producing oscillations varying in amplitudein accordance with sound waves, comprising anodes, grid structure andelectron-emitting means, a source of current representing sound waves,the terminals of said source connect-- ed, respectively, to said anodes,capacities in series with each other bridged across said anodes, aconnection from a point between said capacities to a point intermediatethe terminals of said source, and means coupling the anode and gridcircuits.

' 3. Thermionic oscillation-producing means comprising a source ofcurrent representing sound waves, anodes connected to the differentterminals of said source, grid structure, electron-emitting means, aninductance comprised in a coupling between the anode and grid circuits,capacities in series with each other bridged across said anodes, and aconnection from a point intermediate the terminals of said source and apoint between said capacities to said inductance, said source con-'stituting' the only source of curent in each of v said anode circuits. p

4. Thermionic oscillation-producing means comprising a source of currentrepresenting sound waves, anodes connected to the different terminals ofsaid source, grid structure, electron-emitting means, a connection fromsaid electron-emitting means to a point intermediate said terminals ofsaid source, and means coupling the anode and grid circuits.

In testimony whereof I have hereunto affixed my signature this 11" dayof March,

CORNELIUS D. EHRET.

